The present disclosure provides a process for the preparation of polyester polymers, which may be utilized in the preparation of toner compositions.
Polyester resins may be prepared by a polycondensation process involving the reaction of a diol monomer and a diacid or diester monomer, producing water or an alcohol as a byproduct, which is collected by distillation. Unsaturated polyester resins can be similarly prepared by this process, with the primary exception that the diacid monomer is unsaturated, that is, it includes an alkene segment such as fumaric or maleic acid or diesters thereof.
Unsaturated polyester resins derived from propoxylated Bisphenol-A with fumaric acid are within the purview of those skilled in the art. The propoxylated Bisphenol-A may include, for example, a mixture of monomers prepared by the anionic propoxylation of Bisphenol-A with propylene oxide, in the presence of an alkali hydroxide catalyst in a pressurized vessel, wherein the mixtures obtained are the alkali salts of 4-(2-hydroxyethyl)-Bisphenol-A, bis 4,4′-(2-hydroxyethyl)-Bisphenol-A, and 4-(2′-hydroxyethyl-2-oxyethyl)-4′-(2-hydroxyethyl)-Bisphenol-A.
There exists an alternative condensation method of alkoxylation that can be accomplished by the reaction of a diol with a cyclic alkylene carbonate, wherein Bisphenol-A can be condensed with a cyclic propylene carbonate in the presence of a catalyst and release carbon dioxide as the byproduct at elevated temperatures, thus producing a mixture of propoxylated Bisphenol-A. This latter condensation method has numerous economic advantageous in terms of monomer cost and simplicity.
Electrophotographic toners may include a resin, such as a polyester, a pigment, and optionally a charge control agent. Various toner formulations are within the purview of those skilled in the art, for example, those including a crosslinked unsaturated polyester resin, which may be capable of forming toners having low fixing temperatures and offset properties. Examples of such resins include those disclosed, for example, in U.S. Pat. No. 5,227,460, the disclosure of which is incorporated by reference in its entirety, wherein there is disclosed a poly(propoxylated bisphenol co-fumarate) which is crosslinked to a gel content of up to about 40 weight percent utilizing a peroxide to provide a toner useful for electrophotographic processes.
Other polyesters and processes for their preparation, as well as toners including these polyesters, include those disclosed in U.S. Pat. Nos. 6,291,122, 6,127,080, 6,180,747, 6,063,827, 5,449,719, 5,407,772, 4,788,122, 5,466,554, 5,686,218, 4,988,794, 4,727,011, 4,533,614, 5,366,841, and 5,714,568, the disclosures of each of which are hereby incorporated by reference in their entirety.
Improved methods for producing polyester resins and utilizing same in toner compositions remain desirable.